Origin. - Prepared by saturating a mixture of 2 parts of crystallized, and 3 parts of dried, sodium carbonate with carbon dioxide, generated by the action of hydrochloric acid upon marble. The damp salt formed is shaken with one-half its weight of distilled water, the undissolved portion being dried by exposure to the air.

Description and. Properties. - A white, opaque powder, odorless, and having a cooling, mildly alkaline taste; permanent in dry, but slowly decomposed in moist, air. Soluble in 12 parts of water at 250 C. (770 F.); above that temperature the solution loses carbon dioxide, and at a boiling heat the salt is entirely converted into normal carbonate. Insoluble in alcohol and ether. The drug should be kept in well-closed vessels, in a cool place.

Dose. - 10-30 grains (0.6-2.0 Gm. [15 grains (1 Gm.), U. S. P.].

Official Preparations

Mistura Rhei et Sodae - Misturae Rhei et Sodae - Mixture of Rhubarb and Soda. - Dose, 1/4-2 fluidounces (7.4-59 Cc.) [1 fluidram (4 Cc), U. S. P.].

Trochisci Sodii Bicarbonatis - Trochiscos (acc.) Sodii Bicarbonatis -Troches of Sodium Bicarbonate. - Dose, 1 to 6 troches.

Pulvis Effervescens Compositus - Pulvis Effervescentis Compositi - Compound Effervescent Powder (Seidlitz Powder). - Sodium bicarbonate, 31; potassium and sodium tartrate, 93; tartaric acid, 27.

Dose. - Set of 2 powders. To be dissolved in water separately and then combined and taken while effervescing.